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#REDIRECT ] |
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{{lowercase|title=atoi}} |
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'''atoi''' is a function in the ] that converts a string into an integer numerical representation. <code>atoi</code> stands for ''] to integer''. It is included in the ] ] <code>]</code>. Its prototype is as follows: |
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{{Redirect category shell|1= |
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<source lang="c"> |
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{{R with history}} |
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int atoi(const char *str); |
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{{R to section}} |
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</source> |
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⚫ |
}} |
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The <code>str</code> argument is a string, represented by an array of characters, containing the characters of a signed integer number. The string must be null-terminated. When atoi encounters a string with no numerical sequence, it returns zero (0). |
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There are several variants of the '''atoi''' function, '''atol''', ''']''' and '''atoll''' , which are used to convert a string into a <code>long</code>, <code>double</code>, or <code>long</code> <code>long</code> type, respectively. The '''atoll''' was formerly known as '''atoq''' and was included into ]. |
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==Function Code== |
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/*atoi: convert s to integer*/ |
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int atoi(char s) |
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{ |
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int i, n; |
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n = 0; |
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for(i = 0; s >= '0' && s <= '9'; i++) |
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n = 10 * n + (s - '0') |
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return n; |
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} |
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==Deficiencies== |
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It is impossible to tell whether the string holds valid sequence of digits that represents the number 0 or invalid number as the function returns 0 in both cases. The newer function ] does not have this deficiency. |
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'''atoi''' is neither ], nor ] on some operating systems.<ref name="codecogs_atoi">http://www.codecogs.com/reference/c/stdlib.h/atoi.php</ref> |
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Also, '''atoi''' only converts base ten ascii values (this may also be a benefit depending on perspective). ] and other functions support alternate bases such as hexadecimal and octal. |
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==Standards conformance== |
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The '''atoi''', ], and '''atol''' functions are a part of the ISO standard C library (]), while the '''atoll''' function is added by ]. |
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However, because of the ambiguity in returning 0 and lack of ]ty and ]ty on some operating systems, atoi is considered to be ] by ].<ref name="codecogs_atoi"/> |
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==References== |
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The © 1979 by Bell Telephone Laboratories, Incorporated. |
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The written by ] (November 1971). |
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<references/> |
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==External links== |
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* |
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] |
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] |
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] |
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] |
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] |
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] |
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